Coefficient domain block differential pulse-code modulation in video coding

ABSTRACT

A video decoder may determine, based on syntax elements in a bitstream that comprises an encoded representation of the video data, residual quantized samples of a block of the video data. Additionally, the video decoder may determine quantized residual values based on the residual quantized samples. After determining the quantized residual values, the video decoder may inverse quantize the quantized residual values. The video decoder may generate predicted values by performing intra prediction for the block using unfiltered samples from above or left block boundary samples. Furthermore, the video decoder may reconstruct original sample values of the block based on the inverse-quantized quantized residual values and the prediction values.

This application claims the benefit of U.S. Provisional PatentApplication 62/817,451, filed Mar. 12, 2019, the entire content of whichis incorporated by reference.

TECHNICAL FIELD

This disclosure relates to video encoding and video decoding.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,so-called “smart phones,” video teleconferencing devices, videostreaming devices, and the like. Digital video devices implement videocoding techniques, such as those described in the standards defined byMPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced VideoCoding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), andextensions of such standards. The video devices may transmit, receive,encode, decode, and/or store digital video information more efficientlyby implementing such video coding techniques.

Video coding techniques include spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (e.g., a video picture or a portion of a video picture) maybe partitioned into video blocks, which may also be referred to ascoding tree units (CTUs), coding units (CUs) and/or coding nodes. Videoblocks in an intra-coded (I) slice of a picture are encoded usingspatial prediction with respect to reference samples in neighboringblocks in the same picture. Video blocks in an inter-coded (P or B)slice of a picture may use spatial prediction with respect to referencesamples in neighboring blocks in the same picture or temporal predictionwith respect to reference samples in other reference pictures. Picturesmay be referred to as frames, and reference pictures may be referred toas reference frames.

SUMMARY

In general, this disclosure describes coefficient domain blockdifferential pulse code modulation (BDPCM) methods and relates totechniques related to coefficient level prediction methods for transformskip coding of residual blocks in a video coding process. Thecorresponding entropy encoding process, which is the reverse process ofentropy decoding, is implicitly specified and therefore is part of thetechniques of this disclosure as well. The techniques of this disclosuremay be applied to any of the existing video codecs, such as HighEfficiency Video Coding (HEVC), or be applied as a coding tool to avideo coding standard currently being developed, such as Versatile VideoCoding (VVC), and/or to other future video coding standards.

In one example, this disclosure describes a method of decoding videodata, the method comprising: determining, based on syntax elements in abitstream that comprises an encoded representation of the video data,residual quantized samples of a block of the video data; determiningquantized residual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantizing thequantized residual values; generating predicted values by performingintra prediction for the block using unfiltered samples from above orleft block boundary samples; and reconstructing original sample valuesof the block based on the inverse-quantized quantized residual valuesand the prediction values.

In another example, this disclosure describes a method of encoding videodata, the method comprising: generating a block of predicted values byperforming intra prediction for a block of the video data usingunfiltered samples from above or left block boundary samples; generatingresidual values based on original sample values of the block and thepredicted values; quantizing the residual values; after quantizing theresidual values, determining residual quantized samples based on thequantized residual values; and signaling the residual quantized samples.

In another example, this disclosure describes a device for decodingvideo data, the device comprising: a memory configured to store thevideo data; and one or more processors implemented in circuitry, the oneor more processors configured to: determine, based on syntax elements ina bitstream that comprises an encoded representation of the video data,residual quantized samples of a block of the video data; determinequantized residual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantize thequantized residual values; generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and reconstruct original sample values of theblock based on the inverse-quantized quantized residual values and theprediction values.

In another example, this disclosure describes a device for encodingvideo data, the device comprising: a memory configured to store thevideo data; and one or more processors implemented in circuitry, the oneor more processors configured to: generate a block of predicted valuesby performing intra prediction for a block of the video data usingunfiltered samples from above or left block boundary samples; generateresidual values based on original sample values of the block and thepredicted values; quantize the residual values; after quantizing theresidual values, determine residual quantized samples based on thequantized residual values; and signal the residual quantized samples.

In another example, this disclosure describes a device for decodingvideo data, the device comprising: means for determining, based onsyntax elements in a bitstream that comprises an encoded representationof the video data, residual quantized samples of a block of the videodata; means for determining quantized residual values based on theresidual quantized samples; means for inverse quantizing, afterdetermining the quantized residual values, the quantized residualvalues; means for generating predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and means for reconstructing original samplevalues of the block based on the inverse-quantized quantized residualvalues and the prediction values.

In another example, this disclosure describes a device for encodingvideo data, the device comprising: means for generating a block ofpredicted values by performing intra prediction for a block of the videodata using unfiltered samples from above or left block boundary samples;means for generating residual values based on original sample values ofthe block and the predicted values; means for quantizing the residualvalues; means for determining, after quantizing the residual values,residual quantized samples based on the quantized residual values; andmeans for signaling the residual quantized samples.

In another example, this disclosure describes a computer-readablestorage medium having stored thereon instructions that, when executed,cause one or more processors to: determine, based on syntax elements ina bitstream that comprises an encoded representation of the video data,residual quantized samples of a block of the video data; determinequantized residual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantize thequantized residual values; generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and reconstruct original sample values of theblock based on the inverse-quantized quantized residual values and theprediction values.

In another example, this disclosure describes a computer-readablestorage medium having stored thereon instructions that, when executed,cause one or more processors to: generate a block of predicted values byperforming intra prediction for a block of the video data usingunfiltered samples from above or left block boundary samples; generateresidual values based on original sample values of the block and thepredicted values; quantize the residual values; after quantizing theresidual values, determine residual quantized samples based on thequantized residual values; and signal the residual quantized samples.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may perform the techniques of this disclosure.

FIGS. 2A and 2B are conceptual diagrams illustrating an example quadtreebinary tree (QTBT) structure, and a corresponding coding tree unit(CTU).

FIG. 3 is a block diagram illustrating an example video encoder that mayperform the techniques of this disclosure.

FIG. 4 is a block diagram illustrating an example video decoder that mayperform the techniques of this disclosure.

FIG. 5 is a flowchart illustrating a video encoding process.

FIG. 6 is a flowchart illustrating a video decoding process.

FIG. 7 is a flowchart illustrating an example video encoding processthat includes coefficient domain block-differential pulse-codemodulation (BDPCM), in accordance with one or more techniques of thisdisclosure.

FIG. 8 is a flowchart illustrating an example video decoding processthat includes coefficient domain BDPCM, in accordance with one or moretechniques of this disclosure.

DETAILED DESCRIPTION

In instances where a current block of video data is encoded using intraprediction, it may be advantageous to skip application of a transformthat converts residual data of the current block from a sample domain toa frequency domain. Thus, the video encoder may quantize the residualdata for the block directly. The video encoder may then include, in abitstream, encoded syntax elements representing the quantized residualdata.

Block-based delta pulse code modulation (BDPCM) may improve the encodingefficiency of the residual data of the current block. The video encodermay apply BDPCM in a vertical mode or a horizontal mode. When the videoencoder applies BDPCM in the vertical mode, the video encoder generatespredicted residual samples for a first row of the current block bysubtracting original sample values in the first row of the current blockfrom corresponding reconstructed samples in a bottom row of aneighboring block above the current block. The video encoder may thenquantize and inverse quantize the predicted residual samples for thefirst row of the current block. The video encoder then reconstructs thefirst row of the current block based on the inverse quantized residualvalues for the first row of the current block and the reconstructedsamples in the bottom row of the neighboring block above the currentblock. The video encoder may generate each subsequent row of predictedresidual samples of the current block by subtracting original samplevalues of the row from the reconstructed samples of the row above in thecurrent block. The video encoder may then perform the quantization,inverse quantization, and reconstruction process as before. The videoencoder repeats this process for each row of the current block. For eachrow of the current block, the video encoder includes, in the bitstream,encoded syntax elements representing the quantized residual values forthe row. In the vertical mode, the video encoder performs a similarprocess that works from left to right along columns of the currentblock.

A video decoder receives the encoded syntax elements representing thequantized residual values of the current block. When the current blockis encoded using BDPCM and the vertical mode is used, the video decoderinverse quantizes the quantized residual values of a top row of thecurrent block. The video decoder then reconstructs values of the top rowof the current block by adding the inverse quantized residual values ofthe top row of the current block to corresponding reconstructed samplesof a bottom row of one or more blocks that are above neighbors of thecurrent block. For each respective subsequent rows of the current block,the video decoder inverse quantizes the quantized residual values forthe respective row of the current block and then adds the inversequantized residual values for the row to reconstructed samples of a rowabove the respective row of the current block, thereby reconstructingthe samples of the respective row of the current block. When the currentblock is encoded using BDPCM and the horizontal mode is used, the videodecoder performs a similar process that works from left to right alongcolumns of the current block.

There may be one or more problems with the BDPCM process describedabove. For example, in the above-described BDPCM process (i.e., apixel-domain BDPCM process), the video encoder subtracts samples in thecurrent row or column from reconstructed samples in an adjacent row orcolumn and the video decoder adds samples in the current row or columnfrom reconstructed samples in an adjacent row or column. It isappreciated in this disclosure that the use of reconstructed samples mayslow down and complicate the encoding and decoding processes because thevideo encoder and video decoder may need to wait for inversequantization and reconstruction to occur before being able to determinea predictor for a current row or column of the current block. Hence, inaccordance with a technique of this disclosure, the video encoder andthe video decoder may determine the predicted residual values usingquantized residual values instead of reconstructed samples.

For instance, in one example in accordance with the techniques of thisdisclosure, a video encoder may generate a block of predicted values byperforming intra prediction for a block of the video data using samples(e.g., unfiltered samples) from above or left block boundary samples. Inthis example, the video encoder may generate residual values based onoriginal sample values of the block and the predicted values.Furthermore, the video encoder may quantize the residual values. Afterquantizing the residual values, the video encoder may determine residualquantized samples based on the quantized residual values. The videoencoder may signal the residual quantized samples.

In another example in accordance with the techniques of this disclosure,a video decoder may determine, based on syntax elements in a bitstreamthat comprises an encoded representation of the video data, residualquantized samples of a block of the video data. Additionally, the videodecoder may determine quantized residual values based on the residualquantized samples. After determining the quantized residual values, thevideo decoder may inverse quantize the quantized residual values. Thevideo decoder may also generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples. The video decoder may reconstruct originalsample values of the block based on the inverse-quantized quantizedresidual values and the prediction values.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system 100 that may perform the techniques of this disclosure.The techniques of this disclosure are generally directed to coding(encoding and/or decoding) video data. In general, video data includesany data for processing a video. Thus, video data may include raw,unencoded video, encoded video, decoded (e.g., reconstructed) video, andvideo metadata, such as signaling data.

As shown in FIG. 1, system 100 includes a source device 102 thatprovides encoded video data to be decoded and displayed by a destinationdevice 116, in this example. In particular, source device 102 providesthe video data to destination device 116 via a computer-readable medium110. Source device 102 and destination device 116 may comprise any of awide range of devices, including desktop computers, notebook (i.e.,laptop) computers, tablet computers, set-top boxes, telephone handsetssuch smartphones, televisions, cameras, display devices, computers,mobile devices, broadcast receiver devices, digital media players, videogaming consoles, video streaming device, or the like. In some cases,source device 102 and destination device 116 may be equipped forwireless communication, and thus may be referred to as wirelesscommunication devices.

In the example of FIG. 1, source device 102 includes video source 104,memory 106, video encoder 200, and output interface 108. Destinationdevice 116 includes input interface 122, video decoder 300, memory 120,and display device 118. In accordance with this disclosure, videoencoder 200 of source device 102 and video decoder 300 of destinationdevice 116 may be configured to apply the techniques for coefficientlevel prediction. Thus, source device 102 represents an example of avideo encoding device, while destination device 116 represents anexample of a video decoding device. In other examples, a source deviceand a destination device may include other components or arrangements.For example, source device 102 may receive video data from an externalvideo source, such as an external camera. Likewise, destination device116 may interface with an external display device, rather than includingan integrated display device.

System 100 as shown in FIG. 1 is merely one example. In general, anydigital video encoding and/or decoding device may perform techniques forcoefficient level prediction. Source device 102 and destination device116 are merely examples of such coding devices in which source device102 generates coded video data for transmission to destination device116. This disclosure refers to a “coding” device as a device thatperforms coding (encoding and/or decoding) of data. Thus, video encoder200 and video decoder 300 represent examples of coding devices, inparticular, a video encoder and a video decoder, respectively. In someexamples, source device 102 and destination device 116 may operate in asubstantially symmetrical manner such that each of source device 102 anddestination device 116 includes video encoding and decoding components.Hence, system 100 may support one-way or two-way video transmissionbetween source device 102 and destination device 116, e.g., for videostreaming, video playback, video broadcasting, or video telephony.

In general, video source 104 represents a source of video data (i.e.,raw, uncoded video data) and provides a sequential series of pictures(also referred to as “frames”) of the video data to video encoder 200,which encodes data for the pictures. Video source 104 of source device102 may include a video capture device, such as a video camera, a videoarchive containing previously captured raw video, and/or a video feedinterface to receive video from a video content provider. As a furtheralternative, video source 104 may generate computer graphics-based dataas the source video, or a combination of live video, archived video, andcomputer-generated video. In each case, video encoder 200 encodes thecaptured, pre-captured, or computer-generated video data. Video encoder200 may rearrange the pictures from the received order (sometimesreferred to as “display order”) into a coding order for coding. Videoencoder 200 may generate a bitstream including encoded video data.Source device 102 may then output the encoded video data via outputinterface 108 onto computer-readable medium 110 for reception and/orretrieval by, e.g., input interface 122 of destination device 116.

Memory 106 of source device 102 and memory 120 of destination device 116represent general purpose memories. In some example, memories 106, 120may store raw video data, e.g., raw video from video source 104 and raw,decoded video data from video decoder 300. Additionally oralternatively, memories 106, 120 may store software instructionsexecutable by, e.g., video encoder 200 and video decoder 300,respectively. Although memory 106 and memory 120 are shown separatelyfrom video encoder 200 and video decoder 300 in this example, it shouldbe understood that video encoder 200 and video decoder 300 may alsoinclude internal memories for functionally similar or equivalentpurposes. Furthermore, memories 106, 120 may store encoded video data,e.g., output from video encoder 200 and input to video decoder 300. Insome examples, portions of memories 106, 120 may be allocated as one ormore video buffers, e.g., to store raw, decoded, and/or encoded videodata.

Computer-readable medium 110 may represent any type of medium or devicecapable of transporting the encoded video data from source device 102 todestination device 116. In one example, computer-readable medium 110represents a communication medium to enable source device 102 totransmit encoded video data directly to destination device 116 inreal-time, e.g., via a radio frequency network or computer-basednetwork. Output interface 108 may modulate a transmission signalincluding the encoded video data, and input interface 122 may demodulatethe received transmission signal, according to a communication standard,such as a wireless communication protocol. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device 102 to destination device 116.

In some examples, computer-readable medium 110 may include storagedevice 112. Source device 102 may output encoded data from outputinterface 108 to storage device 112. Similarly, destination device 116may access encoded data from storage device 112 via input interface 122.Storage device 112 may include any of a variety of distributed orlocally accessed data storage media such as a hard drive, Blu-ray discs,DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or anyother suitable digital storage media for storing encoded video data.

In some examples, computer-readable medium 110 may include file server114 or another intermediate storage device that may store the encodedvideo data generated by source device 102. Source device 102 may outputencoded video data to file server 114 or another intermediate storagedevice that may store the encoded video generated by source device 102.Destination device 116 may access stored video data from file server 114via streaming or download. File server 114 may be any type of serverdevice capable of storing encoded video data and transmitting thatencoded video data to the destination device 116. File server 114 mayrepresent a web server (e.g., for a website), a File Transfer Protocol(FTP) server, a content delivery network device, or a network attachedstorage (NAS) device. Destination device 116 may access encoded videodata from file server 114 through any standard data connection,including an Internet connection. This may include a wireless channel(e.g., a Wi-Fi connection), a wired connection (e.g., digital subscriberline (DSL), cable modem, etc.), or a combination of both that issuitable for accessing encoded video data stored on file server 114.File server 114 and input interface 122 may be configured to operateaccording to a streaming transmission protocol, a download transmissionprotocol, or a combination thereof.

Output interface 108 and input interface 122 may represent wirelesstransmitters/receiver, modems, wired networking components (e.g.,Ethernet cards), wireless communication components that operateaccording to any of a variety of IEEE 802.11 standards, or otherphysical components. In examples where output interface 108 and inputinterface 122 comprise wireless components, output interface 108 andinput interface 122 may be configured to transfer data, such as encodedvideo data, according to a cellular communication standard, such as 4G,4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In someexamples where output interface 108 comprises a wireless transmitter,output interface 108 and input interface 122 may be configured totransfer data, such as encoded video data, according to other wirelessstandards, such as an IEEE 802.11 specification, an IEEE 802.15specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. Insome examples, source device 102 and/or destination device 116 mayinclude respective system-on-a-chip (SoC) devices. For example, sourcedevice 102 may include an SoC device to perform the functionalityattributed to video encoder 200 and/or output interface 108, anddestination device 116 may include an SoC device to perform thefunctionality attributed to video decoder 300 and/or input interface122.

The techniques of this disclosure may be applied to video coding insupport of any of a variety of multimedia applications, such asover-the-air television broadcasts, cable television transmissions,satellite television transmissions, Internet streaming videotransmissions, such as dynamic adaptive streaming over HTTP (DASH),digital video that is encoded onto a data storage medium, decoding ofdigital video stored on a data storage medium, or other applications.

Input interface 122 of destination device 116 receives an encoded videobitstream from computer-readable medium 110 (e.g., a communicationmedium, storage device 112, file server 114, or the like). The encodedvideo bitstream may include signaling information defined by videoencoder 200, which is also used by video decoder 300, such as syntaxelements having values that describe characteristics and/or processingof video blocks or other coded units (e.g., slices, pictures, groups ofpictures, sequences, or the like). Display device 118 displays decodedpictures of the decoded video data to a user. Display device 118 mayrepresent any of a variety of display devices such as a cathode ray tube(CRT), a liquid crystal display (LCD), a plasma display, an organiclight emitting diode (OLED) display, or another type of display device.

Although not shown in FIG. 1, in some examples, video encoder 200 andvideo decoder 300 may each be integrated with an audio encoder and/oraudio decoder, and may include appropriate MUX-DEMUX units, or otherhardware and/or software, to handle multiplexed streams including bothaudio and video in a common data stream. If applicable, MUX-DEMUX unitsmay conform to the ITU H.223 multiplexer protocol, or other protocolssuch as the user datagram protocol (UDP).

Video encoder 200 and video decoder 300 each may be implemented as anyof a variety of suitable encoder and/or decoder circuitry, such as oneor more microprocessors, digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), discrete logic, software, hardware, firmware or anycombinations thereof. When the techniques are implemented partially insoftware, a device may store instructions for the software in asuitable, non-transitory computer-readable medium and execute theinstructions in hardware using one or more processors to perform thetechniques of this disclosure. Each of video encoder 200 and videodecoder 300 may be included in one or more encoders or decoders, eitherof which may be integrated as part of a combined encoder/decoder (CODEC)in a respective device. A device including video encoder 200 and/orvideo decoder 300 may comprise an integrated circuit, a microprocessor,and/or a wireless communication device, such as a cellular telephone.

Video encoder 200 and video decoder 300 may operate according to a videocoding standard, such as ITU-T H.265, also referred to as HighEfficiency Video Coding (HEVC) or extensions thereto, such as themulti-view and/or scalable video coding extensions. Alternatively, videoencoder 200 and video decoder 300 may operate according to otherproprietary or industry standards, such as the Joint Exploration TestModel (JEM) or ITU-T H.266, also referred to as Versatile Video Coding(VVC). A recent draft of the VVC standard is described in Bross, et al.“Versatile Video Coding (Draft 4),” Joint Video Experts Team (WET) ofITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 13^(th) Meeting:Marrakech, MA, 9-18 Jan. 2019, JVET-M1001-v5 (hereinafter “VVC Draft4”). The techniques of this disclosure, however, are not limited to anyparticular coding standard.

In general, video encoder 200 and video decoder 300 may performblock-based coding of pictures. The term “block” generally refers to astructure including data to be processed (e.g., encoded, decoded, orotherwise used in the encoding and/or decoding process). For example, ablock may include a two-dimensional matrix of samples of luminanceand/or chrominance data. In general, video encoder 200 and video decoder300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format.That is, rather than coding red, green, and blue (RGB) data for samplesof a picture, video encoder 200 and video decoder 300 may code luminanceand chrominance components, where the chrominance components may includeboth red hue and blue hue chrominance components. In some examples,video encoder 200 converts received RGB formatted data to a YUVrepresentation prior to encoding, and video decoder 300 converts the YUVrepresentation to the RGB format. Alternatively, pre- andpost-processing units (not shown) may perform these conversions.

This disclosure may generally refer to coding (e.g., encoding anddecoding) of pictures to include the process of encoding or decodingdata of the picture. Similarly, this disclosure may refer to coding ofblocks of a picture to include the process of encoding or decoding datafor the blocks, e.g., prediction and/or residual coding. An encodedvideo bitstream generally includes a series of values for syntaxelements representative of coding decisions (e.g., coding modes) andpartitioning of pictures into blocks. Thus, references to coding apicture or a block should generally be understood as coding values forsyntax elements forming the picture or block.

HEVC defines various blocks, including coding units (CUs), predictionunits (PUs), and transform units (TUs). According to HEVC, a video coder(such as video encoder 200) partitions a coding tree unit (CTU) into CUsaccording to a quadtree structure. That is, the video coder partitionsCTUs and CUs into four equal, non-overlapping squares, and each node ofthe quadtree has either zero or four child nodes. Nodes without childnodes may be referred to as “leaf nodes,” and CUs of such leaf nodes mayinclude one or more PUs and/or one or more TUs. The video coder mayfurther partition PUs and TUs. For example, in HEVC, a residual quadtree(RQT) represents partitioning of TUs. In HEVC, PUs representinter-prediction data, while TUs represent residual data. CUs that areintra-predicted include intra-prediction information, such as anintra-mode indication.

As another example, video encoder 200 and video decoder 300 may beconfigured to operate according to JEM or VVC. According to JEM or VVC,a video coder (such as video encoder 200) partitions a picture into aplurality of coding tree units (CTUs). Video encoder 200 may partition aCTU according to a tree structure, such as a quadtree-binary tree (QTBT)structure or Multi-Type Tree (MTT) structure. The QTBT structure removesthe concepts of multiple partition types, such as the separation betweenCUs, PUs, and TUs of HEVC. A QTBT structure includes two levels: a firstlevel partitioned according to quadtree partitioning, and a second levelpartitioned according to binary tree partitioning. A root node of theQTBT structure corresponds to a CTU. Leaf nodes of the binary treescorrespond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using aquadtree (QT) partition, a binary tree (BT) partition, and one or moretypes of triple tree (TT) partitions. A triple tree partition is apartition where a block is split into three sub-blocks. In someexamples, a triple tree partition divides a block into three sub-blockswithout dividing the original block through the center. The partitioningtypes in MTT (e.g., QT, BT, and TT), may be symmetrical or asymmetrical.

In some examples, video encoder 200 and video decoder 300 may use asingle QTBT or MTT structure to represent each of the luminance andchrominance components, while in other examples, video encoder 200 andvideo decoder 300 may use two or more QTBT or MTT structures, such asone QTBT/MTT structure for the luminance component and another QTBT/MTTstructure for both chrominance components (or two QTBT/MTT structuresfor respective chrominance components).

Video encoder 200 and video decoder 300 may be configured to usequadtree partitioning per HEVC, QTBT partitioning, MTT partitioning, orother partitioning structures. For purposes of explanation, thedescription of the techniques of this disclosure is presented withrespect to QTBT partitioning. However, it should be understood that thetechniques of this disclosure may also be applied to video codersconfigured to use quadtree partitioning, or other types of partitioningas well.

This disclosure may use “N×N” and “N by N” interchangeably to refer tothe sample dimensions of a block (such as a CU or other video block) interms of vertical and horizontal dimensions, e.g., 16×16 samples or 16by 16 samples. In general, a 16×16 CU will have 16 samples in a verticaldirection (y=16) and 16 samples in a horizontal direction (x=16).Likewise, an N×N CU generally has N samples in a vertical direction andN samples in a horizontal direction, where N represents a nonnegativeinteger value. The samples in a CU may be arranged in rows and columns.Moreover, CUs need not necessarily have the same number of samples inthe horizontal direction as in the vertical direction. For example, CUsmay comprise N×M samples, where M is not necessarily equal to N.

Video encoder 200 encodes video data for CUs representing predictionand/or residual information, and other information. The predictioninformation indicates how the CU is to be predicted in order to form aprediction block for the CU. The residual information generallyrepresents sample-by-sample differences between samples of the CU priorto encoding and the prediction block.

To predict a CU, video encoder 200 may generally form a prediction blockfor the CU through inter-prediction or intra-prediction.Inter-prediction generally refers to predicting the CU from data of apreviously coded picture, whereas intra-prediction generally refers topredicting the CU from previously coded data of the same picture. Toperform inter-prediction, video encoder 200 may generate the predictionblock using one or more motion vectors. Video encoder 200 may generallyperform a motion search to identify a reference block that closelymatches the CU, e.g., in terms of differences between the CU and thereference block. Video encoder 200 may calculate a difference metricusing a sum of absolute difference (SAD), sum of squared differences(SSD), mean absolute difference (MAD), mean squared differences (MSD),or other such difference calculations to determine whether a referenceblock closely matches the current CU. In some examples, video encoder200 may predict the current CU using uni-directional prediction orbi-directional prediction.

Some examples of JEM and VVC also provide an affine motion compensationmode, which may be considered an inter-prediction mode. In affine motioncompensation mode, video encoder 200 may determine two or more motionvectors that represent non-translational motion, such as zoom in or out,rotation, perspective motion, or other irregular motion types.

To perform intra-prediction, video encoder 200 may select an intraprediction mode to generate the prediction block. Some examples of JEMand VVC provide sixty-seven intra prediction modes, including variousdirectional modes, as well as planar mode and DC mode. In general, videoencoder 200 selects an intra prediction mode that describes neighboringsamples to a current block (e.g., a block of a CU) from which to predictsamples of the current block. Accordingly, such neighboring samples maybe referred to as a predictor. Such samples may generally be above,above and to the left, or to the left of the current block in the samepicture as the current block, assuming video encoder 200 codes CTUs andCUs in raster scan order (left to right, top to bottom).

Directional intra prediction modes correspond to different directions,including a vertical direction and a horizontal direction. To generate aprediction block for a block using a vertical intra prediction mode, avideo coder (e.g., video encoder 200 or video decoder 300) may, for eachsample of the block, determine a predicted value of the sample as thesample in the predictor that is directly above the sample. To generate aprediction block for a block using a horizontal intra prediction, avideo coder (e.g., video encoder 200 or video decoder 300) may, for eachsample of the block, determine a predicted value of the sample as thesample in the predictor that is directly left of the sample.

In some examples, a video coder may apply one or more filters to apredictor before using the predictor for intra prediction of a block.For instance, the video coder may apply a smoothing filter to thepredictor. Application of such filters may improve coding efficiency insome situations. However, in other situations, it may be advantageousnot to apply such filters. Accordingly, in situations where no filter isapplied to the predictor used in intra prediction of a block, thesamples of the predictor may be referred to in this disclosure asunfiltered samples.

Video encoder 200 encodes data representing the prediction mode for acurrent block. For example, for inter-prediction modes, video encoder200 may encode data representing which of the various availableinter-prediction modes is used, as well as motion information for thecorresponding mode. For uni-directional or bi-directionalinter-prediction, for example, video encoder 200 may encode motionvectors using advanced motion vector prediction (AMVP) or merge mode.Video encoder 200 may use similar modes to encode motion vectors foraffine motion compensation mode.

Following prediction, such as intra-prediction or inter-prediction of ablock, video encoder 200 may calculate residual data for the block. Theresidual data, such as a residual block, represents sample by sampledifferences between the block and a prediction block for the block,formed using the corresponding prediction mode. Video encoder 200 mayapply one or more transforms to the residual block, to producetransformed data in a transform domain instead of the sample domain. Forexample, video encoder 200 may apply a discrete cosine transform (DCT),an integer transform, a wavelet transform, or a conceptually similartransform to residual video data. Additionally, video encoder 200 mayapply a secondary transform following the first transform, such as amode-dependent non-separable secondary transform (MDNSST), a signaldependent transform, a Karhunen-Loeve transform (KLT), or the like.

Video encoder 200 produces transform coefficients following applicationof the one or more transforms. In some examples, video encoder 200 mayskip application of the transform. In such cases, residual data may beprocessed in a similar manner as the transform coefficients generated byapplication of the transform. For ease of explanation, steps occurringat video encoder 200 after the point where the transform is applied maybe referred to as the transform domain, regardless of whether videoencoder 200 actually applied the transform. For instance, video encoder200 does not apply the transform when video encoder 200 applies BDPCM.Similarly, steps occurring at video decoder 300 before the point wherean inverse of the transform is applied may be referred to as thetransform domain, regardless of whether the transform was actuallyapplied. For instance, video decoder 300 does not apply the inversetransform when video decoder 300 applies BDPCM.

As noted above, following any transforms to produce transformcoefficients, video encoder 200 may perform quantization of thetransform coefficients. Quantization generally refers to a process inwhich transform coefficients are quantized to possibly reduce the amountof data used to represent the transform coefficients, providing furthercompression. By performing the quantization process, video encoder 200may reduce the bit depth associated with some or all of the transformcoefficients. For example, video encoder 200 may round an n-bit valuedown to an m-bit value during quantization, where n is greater than m.In some examples, to perform quantization, video encoder 200 may performa bitwise right-shift of the value to be quantized.

Following quantization, video encoder 200 may scan the transformcoefficients, producing a one-dimensional vector from thetwo-dimensional matrix including the quantized transform coefficients.The scan may be designed to place higher energy (and therefore lowerfrequency) transform coefficients at the front of the vector and toplace lower energy (and therefore higher frequency) transformcoefficients at the back of the vector. In some examples, video encoder200 may utilize a predefined scan order to scan the quantized transformcoefficients to produce a serialized vector, and then entropy encode thequantized transform coefficients of the vector. In other examples, videoencoder 200 may perform an adaptive scan. After scanning the quantizedtransform coefficients to form the one-dimensional vector, video encoder200 may entropy encode the one-dimensional vector, e.g., according tocontext-adaptive binary arithmetic coding (CABAC). Video encoder 200 mayalso entropy encode values for syntax elements describing metadataassociated with the encoded video data for use by video decoder 300 indecoding the video data.

To perform CABAC, video encoder 200 may assign a context within acontext model to a symbol to be transmitted. The context may relate to,for example, whether neighboring values of the symbol are zero-valued ornot. The probability determination may be based on a context assigned tothe symbol.

Video encoder 200 may further generate syntax data, such as block-basedsyntax data, picture-based syntax data, and sequence-based syntax data,to video decoder 300, e.g., in a picture header, a block header, a sliceheader, or other syntax data, such as a sequence parameter set (SPS),picture parameter set (PPS), or video parameter set (VPS). Video decoder300 may likewise decode such syntax data to determine how to decodecorresponding video data.

In this manner, video encoder 200 may generate a bitstream includingencoded video data, e.g., syntax elements describing partitioning of apicture into blocks (e.g., CUs) and prediction and/or residualinformation for the blocks. Ultimately, video decoder 300 may receivethe bitstream and decode the encoded video data.

In general, video decoder 300 performs a reciprocal process to thatperformed by video encoder 200 to decode the encoded video data of thebitstream. For example, video decoder 300 may decode values for syntaxelements of the bitstream using CABAC in a manner substantially similarto, albeit reciprocal to, the CABAC encoding process of video encoder200. The syntax elements may define partitioning information forpartitioning a picture into CTUs, and partitioning of each CTU accordingto a corresponding partition structure, such as a QTBT structure, todefine CUs of the CTU. The syntax elements may further define predictionand residual information for blocks (e.g., CUs) of video data.

The residual information may be represented by, for example, quantizedtransform coefficients. Video decoder 300 may inverse quantize andinverse transform the quantized transform coefficients of a block toreproduce a residual block for the block. Video decoder 300 uses asignaled prediction mode (intra- or inter-prediction) and relatedprediction information (e.g., motion information for inter-prediction)to form a prediction block for the block. Video decoder 300 may thencombine the prediction block and the residual block (on asample-by-sample basis) to reproduce the original block. Video decoder300 may perform additional processing, such as performing a deblockingprocess to reduce visual artifacts along boundaries of the block.

Abdoli et al., “CE8: BDPCM with horizontal/vertical predictor andindependently decodable areas (test 8.3.1b),” Joint Video Experts Team(JVET) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 13^(th)Meeting, Marrakech, MA, January 2019, document no. JVET-M0057(hereinafter, “JVET-M0057”) described a Block-Differential Pulse-CodeModulation (DPCM) mode that utilizes horizontal or vertical predictionof intra samples that is combined with DPCM coding and transform skipcoding. On the encoder side, for vertical prediction, a top neighboringblock's bottom row pixels are used to perform vertical intra predictionof the first horizontal line of the block with unfiltered predictorsamples. Predicted residuals are quantized, inverse quantized and addedto the predictor to form the predictor for the prediction of the nextline. Video encoder 200 continues this until the end of the block. Forhorizontal prediction, a similar scheme applies except the initialpredictor is from the left neighboring block's last column, the firstcolumn of the block to be coded is predicted, and the residuals arequantized, inverse quantized and added to the predictor to form thepredictor of the next column. Additional, details are described inJVET-M0057. The direction (horizontal/vertical) of BDPCM prediction maybe signaled at a CU level.

Instead of doing the prediction in a pixel domain, as described inWET-M0057, using reconstructed samples from above or left, the presentdisclosure describes quantized level domain prediction in the samedirection. This can be described as follows.

Consider a block of size M (rows)×N (cols). Let r_(i,j), 0≤i≤M−1,0≤j≤N−1 be the prediction residual after performing intra predictionhorizontally (copying left neighbor pixel value across the predictedblock line by line) or vertically (copying top neighbor line to eachline in the predicted block) using unfiltered samples from above or leftblock boundary samples. Assume that the transform is skipped and letQ(r_(i,j)), 0≤i≤M−1, 0≤j≤N−1 denote the quantized version of theresidual r_(i,j), where the residual is the difference between theoriginal block and the predicted block values. Video encoder 200 mayapply the BDPCM to the quantized residual samples as follows: Videoencoder 200 may obtain the modified M×N array {tilde over (R)} withelements {tilde over (r)}_(i,j) according to equation (1) as followswhen vertical BDPCM is signalled:

$\begin{matrix}{{\overset{˜}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},{0 \leq j \leq \left( {N - 1} \right)}} \\{{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},}\ } & {{1 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}}\end{matrix} \right.} & (1)\end{matrix}$

For horizontal prediction, similar rules apply, and video encoder 200may obtain the residual quantized samples by equation (2) as follows:

$\begin{matrix}{{\overset{˜}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},{j = 0}} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)},{1 \leq j \leq \left( {N - 1} \right)}}\end{matrix} \right.} & (2)\end{matrix}$

Video encoder 200 may send the residual quantized samples {tilde over(r)}_(i,j) to video decoder 300.

At video decoder 300, the above calculations are reversed to produceQ(r_(i,j)), 0≤i≤M−1, 0≤j≤N−1. For vertical prediction case, it would beequation (3) below):

Q(r _(i,j))=Σ_(k=0) ^(i) {tilde over (r)} _(k,j), 0≤i≤(M−1),0≤j≤(N−1)  (3)

For horizontal case, it would be equation (4) below:

Q(r _(i,j))=Σ_(k=0) ^(j) {tilde over (r)} _(i,k), 0≤i≤(M−1),0≤j≤(N−1)  (4)

Video decoder 300 may add the inverse-quantized quantized residuals,Q⁻¹(Q(r_(i,j))), to the original prediction values to producereconstructed sample values.

The techniques described in the previous section may requirecompensation of coded transform coefficients with their predictors toderive the coefficient level to be dequantized. This can be done afteran entire block is parsed. In other words, video decoder 300 maycompensate the coded transform coefficients with their predictors aftervideo decoder 300 parses the entire block. If it is required to performthe compensation operation during parsing (i.e., on the fly) and if aseparate buffer is not used for storage of Q(r_(i,j)) values in additionto the {tilde over (r)}_(i,j) values that are parsed, then thedependency of context derivation on neighboring coefficient groups (CGs)(i.e., across CGs) can be disabled for coefficient coding in transformskip mode for various syntax elements representing coefficient values.CGs are M×N groups of non-overlapping sets of transform coefficientswithin a coefficient block. If a part of a context template depends on avalue across its own CG, then those values would be marked unavailableand the context would be derived that way. A context template is aspatial neighborhood from which a video coder gathers information todetermine a coding context. For instance, in an example where a videocoder uses a sum of absolute values of transform coefficients todetermine a coding context, the context template defines the positionsof such transform coefficients, e.g., the context template may define anabove neighbor sample and a left neighbor sample as the samples to usefor determining the coding context. This method allows overwriting ofparsed coefficient values with their compensated (predict and add parsedcoefficient) values to be inverse quantized in the decoder. Thus, it maynot be necessary for video decoder 300 to use a separate buffer to storethe compensated coefficient values. In some examples, the parsedtransform coefficients can be overwritten by their compensated values,and the contexts for future transform coefficients would use theoverwritten values.

This disclosure may generally refer to “signaling” certain information,such as syntax elements. The term “signaling” may generally refer to thecommunication of values for syntax elements and/or other data used todecode encoded video data. That is, video encoder 200 may signal valuesfor syntax elements in the bitstream. In general, signaling refers togenerating a value in the bitstream. As noted above, source device 102may transport the bitstream to destination device 116 substantially inreal time, or not in real time, such as might occur when storing syntaxelements to storage device 112 for later retrieval by destination device116.

FIGS. 2A and 2B are conceptual diagram illustrating an example quadtreebinary tree (QTBT) structure 130, and a corresponding coding tree unit(CTU) 132. The solid lines represent quadtree splitting, and dottedlines indicate binary tree splitting. In each split (i.e., non-leaf)node of the binary tree, one flag is signaled to indicate whichsplitting type (i.e., horizontal or vertical) is used, where 0 indicateshorizontal splitting and 1 indicates vertical splitting in this example.For the quadtree splitting, there is no need to indicate the splittingtype, since quadtree nodes split a block horizontally and verticallyinto 4 sub-blocks with equal size. Accordingly, video encoder 200 mayencode, and video decoder 300 may decode, syntax elements (such assplitting information) for a region tree level (i.e., the first level)of QTBT structure 130 (i.e., the solid lines) and syntax elements (suchas splitting information) for a prediction tree level (i.e., the secondlevel) of QTBT structure 130 (i.e., the dashed lines). Video encoder 200may encode, and video decoder 300 may decode, video data, such asprediction and transform data, for CUs represented by terminal leafnodes of QTBT structure 130.

In general, CTU 132 of FIG. 2B may be associated with parametersdefining sizes of blocks corresponding to nodes of QTBT structure 130 atthe first and second levels. These parameters may include a CTU size(representing a size of CTU 132 in samples), a minimum quadtree size(MinQTSize, representing a minimum allowed quadtree leaf node size), amaximum binary tree size (MaxBTSize, representing a maximum allowedbinary tree root node size), a maximum binary tree depth (MaxBTDepth,representing a maximum allowed binary tree depth), and a minimum binarytree size (MinBTSize, representing the minimum allowed binary tree leafnode size).

The root node of a QTBT structure corresponding to a CTU may have fourchild nodes at the first level of the QTBT structure, each of which maybe partitioned according to quadtree partitioning. That is, nodes of thefirst level are either leaf nodes (having no child nodes) or have fourchild nodes. The example of QTBT structure 130 represents such nodes asincluding the parent node and child nodes having solid lines forbranches. If nodes of the first level are not larger than the maximumallowed binary tree root node size (MaxBTSize), they can be furtherpartitioned by respective binary trees. The binary tree splitting of onenode can be iterated until the nodes resulting from the split reach theminimum allowed binary tree leaf node size (MinBTSize) or the maximumallowed binary tree depth (MaxBTDepth). The example of QTBT structure130 represents such nodes as having dashed lines for branches. Thebinary tree leaf node is referred to as a coding unit (CU), which isused for prediction (e.g., intra-picture or inter-picture prediction)and transform, without any further partitioning. As discussed above, CUsmay also be referred to as “video blocks” or “blocks.”

In one example of the QTBT partitioning structure, the CTU size is setas 128×128 (luma samples and two corresponding 64×64 chroma samples),the MinQTSize is set as 16×16, the MaxBTSize is set as 64×64, theMinBTSize (for both width and height) is set as 4, and the MaxBTDepth isset as 4. The quadtree partitioning is applied to the CTU first togenerate quad-tree leaf nodes. The quadtree leaf nodes may have a sizefrom 16×16 (i.e., the MinQTSize) to 128×128 (i.e., the CTU size). If thequadtree leaf node is 128×128, it will not be further split by thebinary tree, since the size exceeds the MaxBTSize (i.e., 64×64, in thisexample). Otherwise, the quadtree leaf node will be further partitionedby the binary tree. Therefore, the quadtree leaf node is also the rootnode for the binary tree and has the binary tree depth as 0. When thebinary tree depth reaches MaxBTDepth (4, in this example), no furthersplitting is permitted. When the binary tree node has width equal toMinBTSize (4, in this example), it implies that no further verticalsplitting is permitted. Similarly, a binary tree node having a heightequal to MinBTSize implies that no further horizontal splitting ispermitted for that binary tree node. As noted above, leaf nodes of thebinary tree are referred to as CUs and are further processed accordingto prediction and transform without further partitioning.

FIG. 3 is a block diagram illustrating an example video encoder 200 thatmay perform the techniques of this disclosure. FIG. 3 is provided forpurposes of explanation and should not be considered limiting of thetechniques as broadly exemplified and described in this disclosure. Forpurposes of explanation, this disclosure describes video encoder 200 inthe context of video coding standards such as the HEVC video codingstandard and the H.266 (VVC) video coding standard in development.However, the techniques of this disclosure are not limited to thesevideo coding standards and are applicable generally to video encodingand decoding.

In the example of FIG. 3, video encoder 200 includes video data memory230, mode selection unit 202, residual generation unit 204, transformprocessing unit 206, quantization unit 208, inverse quantization unit210, inverse transform processing unit 212, reconstruction unit 214,filter unit 216, decoded picture buffer (DPB) 218, and entropy encodingunit 220. Any or all of video data memory 230, mode selection unit 202,residual generation unit 204, transform processing unit 206,quantization unit 208, inverse quantization unit 210, inverse transformprocessing unit 212, reconstruction unit 214, filter unit 216, DPB 218,and entropy encoding unit 220 may be implemented in one or moreprocessors or in processing circuitry. Moreover, video encoder 200 mayinclude additional or alternative processors or processing circuitry toperform these and other functions.

Video data memory 230 may store video data to be encoded by thecomponents of video encoder 200. Video encoder 200 may receive the videodata stored in video data memory 230 from, for example, video source 104(FIG. 1). DPB 218 may act as a reference picture memory that storesreference video data for use in prediction of subsequent video data byvideo encoder 200. Video data memory 230 and DPB 218 may be formed byany of a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. Video datamemory 230 and DPB 218 may be provided by the same memory device orseparate memory devices. In various examples, video data memory 230 maybe on-chip with other components of video encoder 200, as illustrated,or off-chip relative to those components.

In this disclosure, reference to video data memory 230 should not beinterpreted as being limited to memory internal to video encoder 200,unless specifically described as such, or memory external to videoencoder 200, unless specifically described as such. Rather, reference tovideo data memory 230 should be understood as reference memory thatstores video data that video encoder 200 receives for encoding (e.g.,video data for a current block that is to be encoded). Memory 106 ofFIG. 1 may also provide temporary storage of outputs from the variousunits of video encoder 200.

The various units of FIG. 3 are illustrated to assist with understandingthe operations performed by video encoder 200. The units may beimplemented as fixed-function circuits, programmable circuits, or acombination thereof. Fixed-function circuits refer to circuits thatprovide particular functionality and are preset on the operations thatcan be performed. Programmable circuits refer to circuits that can beprogrammed to perform various tasks and provide flexible functionalityin the operations that can be performed. For instance, programmablecircuits may execute software or firmware that cause the programmablecircuits to operate in the manner defined by instructions of thesoftware or firmware. Fixed-function circuits may execute softwareinstructions (e.g., to receive parameters or output parameters), but thetypes of operations that the fixed-function circuits perform aregenerally immutable. In some examples, one or more of the units may bedistinct circuit blocks (fixed-function or programmable), and in someexamples, the one or more units may be integrated circuits.

Video encoder 200 may include arithmetic logic units (ALUs), elementaryfunction units (EFUs), digital circuits, analog circuits, and/orprogrammable cores, formed from programmable circuits. In examples wherethe operations of video encoder 200 are performed using softwareexecuted by the programmable circuits, memory 106 (FIG. 1) may store theobject code of the software that video encoder 200 receives andexecutes, or another memory within video encoder 200 (not shown) maystore such instructions.

Video data memory 230 is configured to store received video data. Videoencoder 200 may retrieve a picture of the video data from video datamemory 230 and provide the video data to residual generation unit 204and mode selection unit 202. Video data in video data memory 230 may beraw video data that is to be encoded.

Mode selection unit 202 includes a motion estimation unit 222, motioncompensation unit 224, and an intra-prediction unit 226. Mode selectionunit 202 may include additional functional units to perform videoprediction in accordance with other prediction modes. As examples, modeselection unit 202 may include a palette unit, an intra-block copy unit(which may be part of motion estimation unit 222 and/or motioncompensation unit 224), an affine unit, a linear model (LM) unit, or thelike.

Mode selection unit 202 generally coordinates multiple encoding passesto test combinations of encoding parameters and resultingrate-distortion values for such combinations. The encoding parametersmay include partitioning of CTUs into CUs, prediction modes for the CUs,transform types for residual data of the CUs, quantization parametersfor residual data of the CUs, and so on. Mode selection unit 202 mayultimately select the combination of encoding parameters havingrate-distortion values that are better than the other testedcombinations.

Video encoder 200 may partition a picture retrieved from video datamemory 230 into a series of CTUs and encapsulate one or more CTUs withina slice. Mode selection unit 202 may partition a CTU of the picture inaccordance with a tree structure, such as the QTBT structure or thequad-tree structure of HEVC described above. As described above, videoencoder 200 may form one or more CUs from partitioning a CTU accordingto the tree structure. Such a CU may also be referred to generally as a“video block” or “block.”

In general, mode selection unit 202 also controls the components thereof(e.g., motion estimation unit 222, motion compensation unit 224, andintra-prediction unit 226) to generate a prediction block for a currentblock (e.g., a current CU, or in HEVC, the overlapping portion of a PUand a TU). For inter-prediction of a current block, motion estimationunit 222 may perform a motion search to identify one or more closelymatching reference blocks in one or more reference pictures (e.g., oneor more previously coded pictures stored in DPB 218). In particular,motion estimation unit 222 may calculate a value representative of howsimilar a potential reference block is to the current block, e.g.,according to sum of absolute difference (SAD), sum of squareddifferences (SSD), mean absolute difference (MAD), mean squareddifferences (MSD), or the like. Motion estimation unit 222 may generallyperform these calculations using sample-by-sample differences betweenthe current block and the reference block being considered. Motionestimation unit 222 may identify a reference block having a lowest valueresulting from these calculations, indicating a reference block thatmost closely matches the current block.

Motion estimation unit 222 may form one or more motion vectors (MVs)that defines the positions of the reference blocks in the referencepictures relative to the position of the current block in a currentpicture. Motion estimation unit 222 may then provide the motion vectorsto motion compensation unit 224. For example, for uni-directionalinter-prediction, motion estimation unit 222 may provide a single motionvector, whereas for bi-directional inter-prediction, motion estimationunit 222 may provide two motion vectors. Motion compensation unit 224may then generate a prediction block using the motion vectors. Forexample, motion compensation unit 224 may retrieve data of the referenceblock using the motion vector. As another example, if the motion vectorhas fractional sample precision, motion compensation unit 224 mayinterpolate values for the prediction block according to one or moreinterpolation filters. Moreover, for bi-directional inter-prediction,motion compensation unit 224 may retrieve data for two reference blocksidentified by respective motion vectors and combine the retrieved data,e.g., through sample-by-sample averaging or weighted averaging.

As another example, for intra-prediction, or intra-prediction coding,intra-prediction unit 226 may generate the prediction block from samplesneighboring the current block. For example, for directional modes,intra-prediction unit 226 may generally mathematically combine values ofneighboring samples and populate these calculated values in the defineddirection across the current block to produce the prediction block. Asanother example, for DC mode, intra-prediction unit 226 may calculate anaverage of the neighboring samples to the current block and generate theprediction block to include this resulting average for each sample ofthe prediction block.

Mode selection unit 202 provides the prediction block to residualgeneration unit 204. Residual generation unit 204 receives a raw,uncoded version of the current block from video data memory 230 and theprediction block from mode selection unit 202. Residual generation unit204 calculates sample-by-sample differences between the current blockand the prediction block. The resulting sample-by-sample differencesdefine a residual block for the current block. In some examples,residual generation unit 204 may also determine differences betweensample values in the residual block to generate a residual block usingresidual differential pulse code modulation (RDPCM). In some examples,residual generation unit 204 may be formed using one or more subtractorcircuits that perform binary subtraction.

In examples where mode selection unit 202 partitions CUs into PUs, eachPU may be associated with a luma prediction unit and correspondingchroma prediction units. Video encoder 200 and video decoder 300 maysupport PUs having various sizes. As indicated above, the size of a CUmay refer to the size of the luma coding block of the CU and the size ofa PU may refer to the size of a luma prediction unit of the PU. Assumingthat the size of a particular CU is 2N×2N, video encoder 200 may supportPU sizes of 2N×2N or N×N for intra prediction, and symmetric PU sizes of2N×2N, 2N×N, N×2N, N×N, or similar for inter prediction. Video encoder200 and video decoder 300 may also support asymmetric partitioning forPU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

In examples where mode selection unit does not further partition a CUinto PUs, each CU may be associated with a luma coding block andcorresponding chroma coding blocks. As above, the size of a CU may referto the size of the luma coding block of the CU. The video encoder 200and video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

For other video coding techniques such as intra-block copy mode coding,affine-mode coding, and linear model (LM) mode coding, as few asexamples, mode selection unit 202, via respective units associated withthe coding techniques, generates a prediction block for the currentblock being encoded. In some examples, such as palette mode coding, modeselection unit 202 may not generate a prediction block, and insteadgenerate syntax elements that indicate the manner in which toreconstruct the block based on a selected palette. In such modes, modeselection unit 202 may provide these syntax elements to entropy encodingunit 220 to be encoded.

As described above, residual generation unit 204 receives the video datafor the current block and the corresponding prediction block. Residualgeneration unit 204 then generates a residual block for the currentblock. To generate the residual block, residual generation unit 204calculates sample-by-sample differences between the prediction block andthe current block.

Transform processing unit 206 applies one or more transforms to theresidual block to generate a block of transform coefficients (referredto herein as a “transform coefficient block”). Transform processing unit206 may apply various transforms to a residual block to form thetransform coefficient block. For example, transform processing unit 206may apply a discrete cosine transform (DCT), a directional transform, aKarhunen-Loeve transform (KLT), or a conceptually similar transform to aresidual block. In some examples, transform processing unit 206 mayperform multiple transforms to a residual block, e.g., a primarytransform and a secondary transform, such as a rotational transform. Insome examples, transform processing unit 206 does not apply transformsto a residual block. For instance, in examples where a block is codedusing coefficient-domain BDPCM, transform processing unit 206 may skipapplication of the transform to the residual values generated byresidual generation unit 204.

Quantization unit 208 may quantize the transform coefficients in atransform coefficient block, to produce a quantized transformcoefficient block. Quantization unit 208 may quantize transformcoefficients of a transform coefficient block according to aquantization parameter (QP) value associated with the current block.Video encoder 200 (e.g., via mode selection unit 202) may adjust thedegree of quantization applied to the coefficient blocks associated withthe current block by adjusting the QP value associated with the CU.Quantization may introduce loss of information, and thus, quantizedtransform coefficients may have lower precision than the originaltransform coefficients produced by transform processing unit 206.

In accordance with one or more techniques of this disclosure,quantization unit 208 may use coefficient-domain BDPCM to determineresidual quantized samples based on the quantized residual values. Forexample, quantization unit 208 may use equations (1) or (2), above, todetermine the residual quantized samples. Quantization unit 208 maydetermine whether intra-prediction unit 226 used a vertical intraprediction mode or a horizontal intra prediction mode to generate theprediction block that residual generation unit 204 used to generate theresidual values. If intra-prediction unit 226 used the vertical intraprediction mode (i.e., the intra prediction being vertical prediction),quantization unit 208 may use equation (1). If intra-prediction unit 226used the horizontal intra prediction mode (i.e., the intra predictionbeing horizontal prediction), quantization unit 208 may use equation(2). For example, quantization unit 208 may determine whether verticalprediction or horizontal prediction yields greater coding efficiency.

Inverse quantization unit 210 and inverse transform processing unit 212may apply inverse quantization and inverse transforms to a quantizedtransform coefficient block, respectively, to reconstruct a residualblock from the transform coefficient block. In accordance with one ormore examples of this disclosure, if a block is coded usingcoefficient-domain BDPCM, inverse quantization unit 210 may determinequantized residual values based on the residual quantized samples, e.g.,by applying equation (3) or equation (4). More specifically, if theblock was coded using a vertical intra prediction mode, inversequantization unit 210 may apply equation (3). If the block was codedusing a horizontal intra prediction mode, inverse quantization unit 210may apply equation (4). After determining the quantized residual values,inverse quantization unit 210 may inverse quantize the quantizedresidual values.

After inverse quantization unit 210 forms the transform coefficientblock, inverse transform processing unit 212 may apply one or moreinverse transforms to the transform coefficient block to generate aresidual block associated with the current block. For example, inversetransform processing unit 212 may apply an inverse DCT, an inverseinteger transform, an inverse Karhunen-Loeve transform (KLT), an inverserotational transform, an inverse directional transform, or anotherinverse transform to the coefficient block. In examples where a block iscoded using coefficient-domain BDPCM is used, inverse transformprocessing unit 212 may skip application of the inverse transform.

Reconstruction unit 214 may produce a reconstructed block correspondingto the current block (albeit potentially with some degree of distortion)based on the reconstructed residual block and a prediction blockgenerated by mode selection unit 202. For example, reconstruction unit214 may add samples of the reconstructed residual block to correspondingsamples from the prediction block generated by mode selection unit 202to produce the reconstructed block.

Filter unit 216 may perform one or more filter operations onreconstructed blocks. For example, filter unit 216 may performdeblocking operations to reduce blockiness artifacts along edges of CUs.Operations of filter unit 216 may be skipped, in some examples.

Video encoder 200 stores reconstructed blocks in DPB 218. For instance,in examples where operations of filter unit 216 are not needed,reconstruction unit 214 may store reconstructed blocks to DPB 218. Inexamples where operations of filter unit 216 are needed, filter unit 216may store the filtered reconstructed blocks to DPB 218. Motionestimation unit 222 and motion compensation unit 224 may retrieve areference picture from DPB 218, formed from the reconstructed (andpotentially filtered) blocks, to inter-predict blocks of subsequentlyencoded pictures. In addition, intra-prediction unit 226 may usereconstructed blocks in DPB 218 of a current picture to intra-predictother blocks in the current picture.

In general, entropy encoding unit 220 may entropy encode syntax elementsreceived from other functional components of video encoder 200. Forexample, entropy encoding unit 220 may entropy encode quantizedtransform coefficient blocks from quantization unit 208. As anotherexample, entropy encoding unit 220 may entropy encode prediction syntaxelements (e.g., motion information for inter-prediction or intra-modeinformation for intra-prediction) from mode selection unit 202. Entropyencoding unit 220 may perform one or more entropy encoding operations onthe syntax elements, which are another example of video data, togenerate entropy-encoded data. For example, entropy encoding unit 220may perform a context-adaptive variable length coding (CAVLC) operation,a CABAC operation, a variable-to-variable (VV) length coding operation,a syntax-based context-adaptive binary arithmetic coding (SBAC)operation, a Probability Interval Partitioning Entropy (PIPE) codingoperation, an Exponential-Golomb encoding operation, or another type ofentropy encoding operation on the data. In some examples, entropyencoding unit 220 may operate in bypass mode where syntax elements arenot entropy encoded.

Video encoder 200 may output a bitstream that includes the entropyencoded syntax elements needed to reconstruct blocks of a slice orpicture. For instance, in the example of FIG. 3, entropy encoding unit220 may output the bitstream. In accordance with one or more examples ofthis disclosure, video encoder 200 may signal residual quantized samplesin the bitstream. For instance, entropy encoding unit 220 may entropyencode syntax elements representing residual quantized samples andinclude the entropy-encoded syntax elements in the bitstream.

The operations described above are described with respect to a block.Such description should be understood as being operations for a lumacoding block and/or chroma coding blocks. As described above, in someexamples, the luma coding block and chroma coding blocks are luma andchroma components of a CU. In some examples, the luma coding block andthe chroma coding blocks are luma and chroma components of a PU.

In some examples, operations performed with respect to a luma codingblock need not be repeated for the chroma coding blocks. As one example,operations to identify a motion vector (MV) and reference picture for aluma coding block need not be repeated for identifying an MV andreference picture for the chroma blocks. Rather, the MV for the lumacoding block may be scaled to determine the MV for the chroma blocks,and the reference picture may be the same. As another example, theintra-prediction process may be the same for the luma coding blocks andthe chroma coding blocks.

Video encoder 200 represents an example of a device configured to encodevideo data including a memory configured to store video data, and one ormore processing units implemented in circuitry and configured togenerate predicted values by performing intra prediction for a block ofthe video data using unfiltered samples from above or left blockboundary samples; generate residual values based on original samplevalues of the block and the predicted values; quantize the residualvalues; and determine residual quantized samples based on the quantizedresidual values.

FIG. 4 is a block diagram illustrating an example video decoder 300 thatmay perform the techniques of this disclosure. FIG. 4 is provided forpurposes of explanation and is not limiting on the techniques as broadlyexemplified and described in this disclosure. For purposes ofexplanation, this disclosure describes video decoder 300 according tothe techniques of JEM, VVC, and HEVC. However, the techniques of thisdisclosure may be performed by video coding devices that are configuredto other video coding standards.

In the example of FIG. 4, video decoder 300 includes coded picturebuffer (CPB) memory 320, entropy decoding unit 302, predictionprocessing unit 304, inverse quantization unit 306, inverse transformprocessing unit 308, reconstruction unit 310, filter unit 312, anddecoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropydecoding unit 302, prediction processing unit 304, inverse quantizationunit 306, inverse transform processing unit 308, reconstruction unit310, filter unit 312, and DPB 314 may be implemented in one or moreprocessors or in processing circuitry. Moreover, video decoder 300 mayinclude additional or alternative processors or processing circuitry toperform these and other functions.

Prediction processing unit 304 includes motion compensation unit 316 andintra-prediction unit 318. Prediction processing unit 304 may includeadditional units to perform prediction in accordance with otherprediction modes. As examples, prediction processing unit 304 mayinclude a palette unit, an intra-block copy unit (which may form part ofmotion compensation unit 316), an affine unit, a linear model (LM) unit,or the like. In other examples, video decoder 300 may include more,fewer, or different functional components.

CPB memory 320 may store video data, such as an encoded video bitstream,to be decoded by the components of video decoder 300. The video datastored in CPB memory 320 may be obtained, for example, fromcomputer-readable medium 110 (FIG. 1). CPB memory 320 may include a CPBthat stores encoded video data (e.g., syntax elements) from an encodedvideo bitstream. Also, CPB memory 320 may store video data other thansyntax elements of a coded picture, such as temporary data representingoutputs from the various units of video decoder 300. DPB 314 generallystores decoded pictures, which video decoder 300 may output and/or useas reference video data when decoding subsequent data or pictures of theencoded video bitstream. CPB memory 320 and DPB 314 may be formed by anyof a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. CPB memory 320and DPB 314 may be provided by the same memory device or separate memorydevices. In various examples, CPB memory 320 may be on-chip with othercomponents of video decoder 300, or off-chip relative to thosecomponents.

Additionally or alternatively, in some examples, video decoder 300 mayretrieve coded video data from memory 120 (FIG. 1). That is, memory 120may store data as discussed above with CPB memory 320. Likewise, memory120 may store instructions to be executed by video decoder 300, whensome or all of the functionality of video decoder 300 is implemented insoftware to be executed by processing circuitry of video decoder 300.

The various units shown in FIG. 4 are illustrated to assist withunderstanding the operations performed by video decoder 300. The unitsmay be implemented as fixed-function circuits, programmable circuits, ora combination thereof. Similar to FIG. 3, fixed-function circuits referto circuits that provide particular functionality, and are preset on theoperations that can be performed. Programmable circuits refer tocircuits that can be programmed to perform various tasks and provideflexible functionality in the operations that can be performed. Forinstance, programmable circuits may execute software or firmware thatcause the programmable circuits to operate in the manner defined byinstructions of the software or firmware. Fixed-function circuits mayexecute software instructions (e.g., to receive parameters or outputparameters), but the types of operations that the fixed-functioncircuits perform are generally immutable. In some examples, one or moreof the units may be distinct circuit blocks (fixed-function orprogrammable), and in some examples, the one or more units may beintegrated circuits.

Video decoder 300 may include ALUs, EFUs, digital circuits, analogcircuits, and/or programmable cores formed from programmable circuits.In examples where the operations of video decoder 300 are performed bysoftware executing on the programmable circuits, on-chip or off-chipmemory may store instructions (e.g., object code) of the software thatvideo decoder 300 receives and executes.

Entropy decoding unit 302 may receive encoded video data from the CPBand entropy decode the video data to reproduce syntax elements.Prediction processing unit 304, inverse quantization unit 306, inversetransform processing unit 308, reconstruction unit 310, and filter unit312 may generate decoded video data based on the syntax elementsextracted from the bitstream.

In general, video decoder 300 reconstructs a picture on a block-by-blockbasis. Video decoder 300 may perform a reconstruction operation on eachblock individually (where the block currently being reconstructed, i.e.,decoded, may be referred to as a “current block”).

Entropy decoding unit 302 may entropy decode syntax elements definingquantized transform coefficients of a quantized transform coefficientblock, as well as transform information, such as a quantizationparameter (QP) and/or transform mode indication(s). Inverse quantizationunit 306 may use the QP associated with the quantized transformcoefficient block to determine a degree of quantization and, likewise, adegree of inverse quantization for inverse quantization unit 306 toapply. Inverse quantization unit 306 may, for example, perform a bitwiseleft-shift operation to inverse quantize the quantized transformcoefficients. Inverse quantization unit 306 may thereby form a transformcoefficient block including transform coefficients.

In accordance with one or more techniques of this disclosure, inversequantization unit 306 may determine, based on syntax elements obtainedby entropy decoding unit 302 from a bitstream, residual quantizedsamples of a block of the video data. Additionally, inverse quantizationunit 306 may determine quantized residual values based on the residualquantized samples. For instance, inverse quantization unit 306 may applyequations (3) or (4) to determine the quantized residual values. Morespecifically, if the block was coded using a vertical intra predictionmode, inverse quantization unit 306 may apply equation (3). If the blockwas coded using a horizontal intra prediction mode, inverse quantizationunit 306 may apply equation (4). After determining the quantizedresidual values, inverse quantization unit 306 may inverse quantize thequantized residual values.

After inverse quantization unit 306 forms the transform coefficientblock, inverse transform processing unit 308 may apply one or moreinverse transforms to the transform coefficient block to generate aresidual block associated with the current block. For example, inversetransform processing unit 308 may apply an inverse DCT, an inverseinteger transform, an inverse Karhunen-Loeve transform (KLT), an inverserotational transform, an inverse directional transform, or anotherinverse transform to the transform coefficient block. In examples wherea block is coded using coefficient-domain BDPCM is used, inversetransform processing unit 308 may skip application of the inversetransform.

Furthermore, prediction processing unit 304 generates a prediction blockaccording to prediction information syntax elements that were entropydecoded by entropy decoding unit 302. For example, if the predictioninformation syntax elements indicate that the current block isinter-predicted, motion compensation unit 316 may generate theprediction block. In this case, the prediction information syntaxelements may indicate a reference picture in DPB 314 from which toretrieve a reference block, as well as a motion vector identifying alocation of the reference block in the reference picture relative to thelocation of the current block in the current picture. Motioncompensation unit 316 may generally perform the inter-prediction processin a manner that is substantially similar to that described with respectto motion compensation unit 224 (FIG. 3).

As another example, if the prediction information syntax elementsindicate that the current block is intra-predicted, intra-predictionunit 318 may generate the prediction block according to anintra-prediction mode indicated by the prediction information syntaxelements. Again, intra-prediction unit 318 may generally perform theintra-prediction process in a manner that is substantially similar tothat described with respect to intra-prediction unit 226 (FIG. 3).Intra-prediction unit 318 may retrieve data of neighboring samples tothe current block from DPB 314.

Reconstruction unit 310 may reconstruct the current block using theprediction block and the residual block. For example, reconstructionunit 310 may add samples of the residual block to corresponding samplesof the prediction block to reconstruct the current block.

Filter unit 312 may perform one or more filter operations onreconstructed blocks. For example, filter unit 312 may performdeblocking operations to reduce blockiness artifacts along edges of thereconstructed blocks. Operations of filter unit 312 are not necessarilyperformed in all examples.

Video decoder 300 may store the reconstructed blocks in DPB 314. Forinstance, in examples where operations of filter unit 312 are notperformed, reconstruction unit 310 may store reconstructed blocks to DPB314. In examples where operations of filter unit 312 are performed,filter unit 312 may store the filtered reconstructed blocks to DPB 314.As discussed above, DPB 314 may provide reference information, such assamples of a current picture for intra-prediction and previously decodedpictures for subsequent motion compensation, to prediction processingunit 304. Moreover, video decoder 300 may output decoded pictures fromDPB for subsequent presentation on a display device, such as displaydevice 118 of FIG. 1.

In this manner, video decoder 300 represents an example of a videodecoding device including a memory configured to store video data, andone or more processing units implemented in circuitry and configured todetermine, based on syntax elements in a bitstream that comprises anencoded representation of the video data, residual quantized samples ofa block of the video data; determine quantized residual values based onthe residual quantized samples; inverse quantize the quantized residualvalues; generate predicted values by performing intra prediction for theblock using unfiltered samples from above or left block boundarysamples; and reconstruct original sample values of the block based onthe inverse-quantized quantized residuals and the prediction values.

In the example of FIG. 4, entropy decoding unit 302 of video decoder 300may determine, based on syntax elements in a bitstream that comprises anencoded representation of the video data, residual quantized samples ofa block of the video data. Furthermore, in the example of FIG. 4, videodecoder 300 may determine quantized residual values based on theresidual quantized samples; inverse quantize the quantized residualvalues; generate predicted values by performing intra prediction for theblock using unfiltered samples from above or left block boundarysamples; and reconstruct original sample values of the block based onthe inverse-quantized quantized residuals and the prediction values.

FIG. 5 is a flowchart illustrating an example method for encoding acurrent block. The current block may comprise a current CU. Althoughdescribed with respect to video encoder 200 (FIGS. 1 and 2), it shouldbe understood that other devices may be configured to perform a methodsimilar to that of FIG. 5.

In this example, video encoder 200 initially predicts the current block(350). For example, video encoder 200 may form a prediction block forthe current block. Video encoder 200 may then calculate a residual blockfor the current block (352). To calculate the residual block, videoencoder 200 may calculate a difference between the original, uncodedblock and the prediction block for the current block. Video encoder 200may then transform difference values to produce transform coefficientsand quantize the transform coefficients of the residual block (354). Inaccordance with the techniques of this disclosure, video encoder 200 mayskip application of the transform and may perform coefficient-domainBDPCM using the quantized residual values. Next, video encoder 200 mayscan the quantized transform coefficients (or quantized residual valueswhen video encoder 200 applies coefficient-domain BDPCM) of the residualblock (356). During the scan, or following the scan, video encoder 200may entropy encode the transform coefficients (or quantized residualvalues when video encoder 200 applies coefficient-domain BDPCM) (358).For example, video encoder 200 may encode the transform coefficients (orquantized residual values when video encoder 200 appliescoefficient-domain BDPCM) using CAVLC or CABAC. Video encoder 200 maythen output the entropy encoded data of the block (360). Thus, inexamples where video encoder 200 applies coefficient-domain BDPCM, videoencoder 200 may signal the residual quantized values.

FIG. 6 is a flowchart illustrating an example method for decoding acurrent block of video data. The current block may comprise a currentCU. Although described with respect to video decoder 300 (FIGS. 1 and3), it should be understood that other devices may be configured toperform a method similar to that of FIG. 6.

Video decoder 300 may receive entropy coded data for the current block,such as entropy coded prediction information and entropy coded data fortransform coefficients of a residual block corresponding to the currentblock (370). Video decoder 300 may entropy decode the entropy coded datato determine prediction information for the current block and toreproduce transform coefficients of the residual block (372). Videodecoder 300 may predict the current block (374), e.g., using an intra-or inter-prediction mode as indicated by the prediction information forthe current block, to calculate a prediction block for the currentblock. Video decoder 300 may then inverse scan the reproduced transformcoefficients (376), to create a block of quantized transformcoefficients. Video decoder 300 may then inverse quantize and apply andinverse transform to the transform coefficients to produce a residualblock (378). Video decoder 300 may perform the techniques of thisdisclosure for coefficient-domain BDPCM as part of the step of producingthe residual block. Video decoder 300 may ultimately decode the currentblock by combining the prediction block and the residual block (380).

FIG. 7 is a flowchart illustrating an example video encoding processthat includes coefficient domain block-differential pulse-codemodulation (BDPCM), in accordance with one or more techniques of thisdisclosure. FIG. 7 may be a more specific instance of the operation ofFIG. 5 in which video encoder 200 uses coefficient-domain BDPCM. In theexample of FIG. 7, video encoder 200 may generate a block of predictedvalues by performing intra prediction for a block of the video datausing unfiltered samples from above or left block boundary samples(700). For instance, video encoder 200 may perform intra prediction inaccordance with any of the examples provided elsewhere in thisdisclosure.

Additionally, video encoder 200 may generate residual values based onoriginal sample values of the block and the predicted values (702). Eachof the residual values may indicate a difference between one of theoriginal sample values of the block and a corresponding predicted value.

Furthermore, in the example of FIG. 7, video encoder 200 may quantizethe residual values (704). For example, video encoder 200 may quantizethe residual values in accordance with any of the examples forquantizing described elsewhere in this disclosure.

After quantizing the residual values, video encoder 200 may determineresidual quantized samples based on the quantized residual values (706).In examples where the intra prediction is vertical prediction, videoencoder 200 may determine the residual quantized samples as:

${\overset{˜}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},{0 \leq j \leq \left( {N - 1} \right)}} \\{{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},}\ } & {{1 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}}\end{matrix} \right.$

where {tilde over (r)}_(k,j) is a residual quantized sample at positioni,j, Q(r_(i,j)) and Q(r_((i−1),j)) are quantized residual values, M is anumber of rows of the block, and N is a number of columns of the block.In examples where intra prediction is horizontal prediction, videoencoder 200 may determine the residual quantized samples as:

${\overset{˜}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},{j = 0}} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)},{1 \leq j \leq \left( {N - 1} \right)}}\end{matrix} \right.$

where {tilde over (r)}_(k,j) is a residual quantized sample at positioni,j, Q(r_(i,j)) and Q(r_((i−1),j)) are quantized residual values, M is anumber of rows of the block, and N is a number of columns of the block.

Video encoder 200 may signal the residual quantized samples (708). Forexample, video encoder 200 may include entropy-encoded syntax elementsrepresent the residual quantized samples in a bitstream.

FIG. 8 is a flowchart illustrating an example video decoding processthat includes coefficient domain BDPCM, in accordance with one or moretechniques of this disclosure. FIG. 8 may be a more specific instance ofthe operation of FIG. 5 in which video encoder 200 usescoefficient-domain BDPCM. In the example of FIG. 8, video decoder 300may determine, based on syntax elements in a bitstream that comprises anencoded representation of the video data, residual quantized samples ofa block of the video data (800). For example, video decoder 300 may useentropy decoding to decode syntax elements in a bitstream that indicatethe residual quantized samples of the block.

Furthermore, in the example of FIG. 8, video decoder 300 may determinequantized residual values based on the residual quantized samples (802).In examples where the intra prediction is vertical prediction, videodecoder 300 may determine the quantized residual values as:

${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{i}{\overset{˜}{r}}_{k,j}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$

where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block. Inexamples where the intra prediction is horizontal prediction, videodecoder 300 may determine the quantized residual values as:

${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{j}{\overset{˜}{r}}_{i,k}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$

where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.

After determining the quantized residual values, video decoder 300 mayinverse quantize the quantized residual values (804). For example, videodecoder 300 may inverse quantize the quantized residual values byinversing any of the examples of quantization provided elsewhere in thisdisclosure.

Video decoder 300 may generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples (806). For instance, video decoder 300 mayperform intra prediction in accordance with any of the examples providedelsewhere in this disclosure.

Video decoder 300 may reconstruct original sample values of the blockbased on the inverse-quantized quantized residual values and theprediction values (808). For example, video decoder 300 may addinverse-quantized quantized residual values to corresponding predictionvalues to reconstruct the original sample values.

The following paragraphs provide a non-limiting list of enumeratedexamples in accordance with the techniques of this disclosure.

EXAMPLE 1

A method of decoding video data, the method comprising: determining,based on syntax elements in a bitstream that comprises an encodedrepresentation of the video data, residual quantized samples of a blockof the video data; determining quantized residual values based on theresidual quantized samples; inverse quantizing the quantized residualvalues; generating predicted values by performing intra prediction forthe block using unfiltered samples from above or left block boundarysamples; and reconstructing original sample values of the block based onthe inverse-quantized quantized residuals and the prediction values.

EXAMPLE 2

The method of example 1, wherein determining the quantized residualvalues comprises: based on the intra prediction being verticalprediction, determining the quantized residual values as:

${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{i}{\overset{˜}{r}}_{k,j}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$

where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.

EXAMPLE 3

The method of example 1, wherein determining the quantized residualvalues comprises: based on the intra prediction being horizontalprediction, determining the quantized residual values as:

${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{j}{\overset{\sim}{r}}_{i,k}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$

where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.

EXAMPLE 4

A method of encoding video data, the method comprising: generatingpredicted values by performing intra prediction for a block of the videodata using unfiltered samples from above or left block boundary samples;generating residual values based on original sample values of the blockand the predicted values; quantizing the residual values; anddetermining residual quantized samples based on the quantized residualvalues.

EXAMPLE 5

The method of example 4, wherein determining the residual quantizedsamples comprises: based on the intra prediction being verticalprediction, determining the quantized residuals as:

${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)}\ ,} & {{i = 0},} & {0 \leq j \leq \left( {N - 1} \right)} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}}\ ,} & {{1 \leq i \leq \left( {M - 1} \right)}\ ,} & {0 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$

where {tilde over (r)}_(k,j) is a residual quantized sample at positioni,j, Q(r_(i,j)) and Q(r_((i−1),j)) are quantized residual values, M is anumber of rows of the block, and N is a number of columns of the block.

EXAMPLE 6

The method of example 4, wherein determining the quantized residualscomprises: based on the intra prediction being horizontal prediction,determining the quantized residuals as:

${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)}\ ,} & {{0 \leq i \leq \left( {M - 1} \right)}\ ,} & {j = 0} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{i,{O - 1}})} \right)}}\ ,} & {{0 \leq i \leq \left( {M - 1} \right)}\ ,} & {1 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$

where {tilde over (r)}_(k,j) is a residual quantized sample at positioni,j, Q(r_(i,j)) and Q(r_((i−1),j)) are quantized residual values, M is anumber of rows of the block, and N is a number of columns of the block.

EXAMPLE 7

A device for coding video data, the device comprising one or more meansfor performing the method of any of examples 1-6.

EXAMPLE 8

The device of example 7, wherein the one or more means comprise one ormore processors implemented in circuitry.

EXAMPLE 9

The device of any of examples 7 and 8, further comprising a memory tostore the video data.

EXAMPLE 10

The device of any of examples 7-9, further comprising a displayconfigured to display decoded video data.

EXAMPLE 11

The device of any of examples 7-10, wherein the device comprises one ormore of a camera, a computer, a mobile device, a broadcast receiverdevice, or a set-top box.

EXAMPLE 12

The device of any of examples 7-11, wherein the device comprises a videodecoder.

EXAMPLE 13

The device of any of examples 7-12, wherein the device comprises a videoencoder.

EXAMPLE 14

A computer-readable storage medium having stored thereon instructionsthat, when executed, cause one or more processors to perform the methodof any of examples 1-6.

EXAMPLE 15

A device for encoding video data, the device comprising means forperforming the methods of any of examples 1-6.

It is to be recognized that depending on the example, certain acts orevents of any of the techniques described herein can be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,not all described acts or events are necessary for the practice of thetechniques). Moreover, in certain examples, acts or events may beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors, rather than sequentially.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the terms “processor” and “processing circuity,”as used herein may refer to any of the foregoing structures or any otherstructure suitable for implementation of the techniques describedherein. In addition, in some aspects, the functionality described hereinmay be provided within dedicated hardware and/or software modulesconfigured for encoding and decoding, or incorporated in a combinedcodec. Also, the techniques could be fully implemented in one or morecircuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of decoding video data, the methodcomprising: determining, based on syntax elements in a bitstream thatcomprises an encoded representation of the video data, residualquantized samples of a block of the video data; determining quantizedresidual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantizing thequantized residual values; generating predicted values by performingintra prediction for the block using unfiltered samples from above orleft block boundary samples; and reconstructing original sample valuesof the block based on the inverse-quantized quantized residual valuesand the prediction values.
 2. The method of claim 1, wherein determiningthe quantized residual values comprises: based on the intra predictionbeing vertical prediction, determining the quantized residual values as:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{i}{\overset{\sim}{r}}_{k,j}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 3. Themethod of claim 1, wherein determining the quantized residual valuescomprises: based on the intra prediction being horizontal prediction,determining the quantized residual values as:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{j}{\overset{\sim}{r}}_{i,k}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 4. Amethod of encoding video data, the method comprising: generating a blockof predicted values by performing intra prediction for a block of thevideo data using unfiltered samples from above or left block boundarysamples; generating residual values based on original sample values ofthe block and the predicted values; quantizing the residual values;after quantizing the residual values, determining residual quantizedsamples based on the quantized residual values; and signaling theresidual quantized samples.
 5. The method of claim 4, whereindetermining the residual quantized samples comprises: based on the intraprediction being vertical prediction, determining the residual quantizedsamples as: ${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},} & {0 \leq j \leq \left( {N - 1} \right)} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},} & {{1 \leq i \leq \left( {M - 1} \right)}\ ,} & {0 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 6. The method of claim 4, whereindetermining the quantized residual values comprises: based on the intraprediction being horizontal prediction, determining the residualquantized samples as:${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},} & {j = 0} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)}\ ,} & {1 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 7. A device for decoding video data,the device comprising: a memory configured to store the video data; andone or more processors implemented in circuitry, the one or moreprocessors configured to: determine, based on syntax elements in abitstream that comprises an encoded representation of the video data,residual quantized samples of a block of the video data; determinequantized residual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantize thequantized residual values; generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and reconstruct original sample values of theblock based on the inverse-quantized quantized residual values and theprediction values.
 8. The device of claim 7, wherein the one or moreprocessors, are configured such that, as part of determining thequantized residual values, the one or more processors: based on theintra prediction being vertical prediction, determine the quantizedresidual values as:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{i}{\overset{\sim}{r}}_{k,j}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i, j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 9. Thedevice of claim 7, wherein the one or more processors are configuredsuch that, as part of determining the quantized residual values, the oneor more processors: based on the intra prediction being horizontalprediction, determine the quantized residual values as:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{j}{\overset{\sim}{r}}_{i,k}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 10. Thedevice of claim 7, further comprising a display configured to displaydecoded video data.
 11. The device of claim 7, wherein the devicecomprises one or more of a camera, a computer, a mobile device, abroadcast receiver device, or a set-top box.
 12. A device for encodingvideo data, the device comprising: a memory configured to store thevideo data; and one or more processors implemented in circuitry, the oneor more processors configured to: generate a block of predicted valuesby performing intra prediction for a block of the video data usingunfiltered samples from above or left block boundary samples; generateresidual values based on original sample values of the block and thepredicted values; quantize the residual values; after quantizing theresidual values, determine residual quantized samples based on thequantized residual values; and signal the residual quantized samples.13. The device of claim 12, wherein the one or more processors areconfigured such that, as part of determining the residual quantizedsamples, the one or more processors: based on the intra prediction beingvertical prediction, determine the residual quantized samples as:${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},} & {0 \leq j \leq \left( {N - 1} \right)} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},} & {{1 \leq i \leq \left( {M - 1} \right)},} & {0 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 14. The device of claim 12, whereinthe one or more processors are configured such that, as part ofdetermining the quantized residual values, the one or more processors:based on the intra prediction being horizontal prediction, determine theresidual quantized samples as:${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},} & {j = 0} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)},} & {1 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 15. The device of claim 12, whereinthe device comprises one or more of a camera, a computer, a mobiledevice, a broadcast receiver device, or a set-top box.
 16. A device fordecoding video data, the device comprising: means for determining, basedon syntax elements in a bitstream that comprises an encodedrepresentation of the video data, residual quantized samples of a blockof the video data; means for determining quantized residual values basedon the residual quantized samples; means for inverse quantizing, afterdetermining the quantized residual values, the quantized residualvalues; means for generating predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and means for reconstructing original samplevalues of the block based on the inverse-quantized quantized residualvalues and the prediction values.
 17. The device of claim 16, whereinthe means for determining the quantized residual values comprises: meansfor determining, based on the intra prediction being verticalprediction, the quantized residual values as:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{i}{\overset{\sim}{r}}_{k,j}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 18. Thedevice of claim 16, wherein the means for determining the quantizedresidual values comprises: means for determining, based on the intraprediction being horizontal prediction, the quantized residual valuesas:${{Q\left( r_{i,j} \right)} = {\sum\limits_{k = 0}^{j}{\overset{\sim}{r}}_{i,k}}},{0 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}$where Q(r_(i,j)) is a quantized residual value at position i,j, {tildeover (r)}_(k,j) is one of the residual quantized samples, M is a numberof rows of the block, and N is a number of columns of the block.
 19. Adevice for encoding video data, the device comprising: means forgenerating a block of predicted values by performing intra predictionfor a block of the video data using unfiltered samples from above orleft block boundary samples; means for generating residual values basedon original sample values of the block and the predicted values; meansfor quantizing the residual values; means for determining, afterquantizing the residual values, residual quantized samples based on thequantized residual values; and means for signaling the residualquantized samples.
 20. The device of claim 19, wherein the means fordetermining the residual quantized samples comprises: means fordetermining, based on the intra prediction being vertical prediction,the residual quantized samples as:${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},} & {0 \leq j \leq \left( {N - 1} \right)} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},} & {{1 \leq i \leq \left( {M - 1} \right)},} & {0 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 21. The device of claim 19, whereinthe means for determining the quantized residual values comprises: meansfor determining, based on the intra prediction being horizontalprediction, the residual quantized samples as:${\overset{\sim}{r}}_{i,j} = \left\{ \begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},} & {j = 0} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)},} & {1 \leq j \leq \left( {N - 1} \right)}\end{matrix} \right.$ where {tilde over (r)}_(k,j) is a residualquantized sample at position i,j, Q(r_(i,j)) and Q(r_((i−1),j)) arequantized residual values, M is a number of rows of the block, and N isa number of columns of the block.
 22. A computer-readable storage mediumhaving stored thereon instructions that, when executed, cause one ormore processors to: determine, based on syntax elements in a bitstreamthat comprises an encoded representation of the video data, residualquantized samples of a block of the video data; determine quantizedresidual values based on the residual quantized samples; afterdetermining the quantized residual values, inverse quantize thequantized residual values; generate predicted values by performing intraprediction for the block using unfiltered samples from above or leftblock boundary samples; and reconstruct original sample values of theblock based on the inverse-quantized quantized residual values and theprediction values.
 23. A computer-readable storage medium having storedthereon instructions that, when executed, cause one or more processorsto: generate a block of predicted values by performing intra predictionfor a block of the video data using unfiltered samples from above orleft block boundary samples; generate residual values based on originalsample values of the block and the predicted values; quantize theresidual values; after quantizing the residual values, determineresidual quantized samples based on the quantized residual values; andsignal the residual quantized samples.